Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$205.85	10.874%	$228.2341	$228.23	$228.25	$228.20
Purchase #2	$93.35	7.669%	$100.509	$100.51	$100.50	$100.50
Purchase #3	$102.45	6.741%	$109.3562	$109.36	$109.35	$109.40
Purchase #4	$66.41	13.500%	$75.3754	$75.38	$75.40	$75.40
Purchase #5	$158.55	5.815%	$167.7697	$167.77	$167.75	$167.80
Purchase #6	$237.35	3.871%	$246.5378	$246.54	$246.55	$246.50
Purchase #7	$171.51	9.803%	$188.3231	$188.32	$188.30	$188.30
7 purchase totals =	$1,035.47		$1,116.1053	$1,116.11	$1,116.10	$1,116.10